Working machines, such as excavators and the like, are often designed to be able to work with different types of tools. Change from one tool to another involves different types of connections, mechanic, hydraulic and electric. Usually, the operation of the tools is essentially hydraulic. In order to facilitate change of tools, it is since long previously known with different types of quick-coupling systems for the hydraulics. These may be automatic to different extents, and it is desirable that switching can be effected without the operator unnecessarily needing to leave the driver's cab.
In connection with semi-manual or fully automatic multi-coupling systems for the interconnection of a plurality of hydraulic hoses, it is important that one of the coupling units is safely and firmly fastened together with the attaching element thereof such as a holder block. In such multi-coupling systems, the principle of function is that one of the coupling units is fixedly assembled with a holder block and the other coupling unit is flexibly attached in the attaching element thereof so as to be able to absorb play and manufacturing tolerances of the system. The coupling units consist of a female coupling unit and a male coupling unit. Usually, but not always, it is the female coupling unit that is fixedly mounted and the male coupling unit flexibly. It is important to secure a proper attachment of the fixed coupling unit. The development of the hydraulic field moves fast toward higher working pressure, which implies increased separation forces between the coupling units and thereby greater stresses on their attachment. Increased use of tools in the form of steel scissors, hydraulic hammers, vibrator carriages, screening buckets, etc., gives pulsations in the hydraulic system of the tool carrier, which also makes great demands on the attachments of the coupling units.
Another problem that often occurs is that it is narrow and lack of space between the different couplings. This is because there is a continuously increased demand of more functions and higher oil flows, which in turn means desires of larger coupling dimensions, etc. The space and room for mounting tools in connection with mounting and dismounting of couplings and hose connections is another limiting factor.
The fixedly mounted coupling unit—in the following called the female coupling unit, since usually, it is this that is fixedly mounted—is normally installed in the holder block in a hole in the same, the hose-connection end of the coupling unit being situated on one side of the holder block and the nose end thereof, i.e., the end to be interconnected with a male coupling unit, is situated on the opposite end of the holder block.
In that connection, there are different alternatives for the installation of the female coupling unit into the holder block.
A first possibility is to mount the coupling unit in place by means of circlip at the nose end thereof. The advantage of this method is that it is inexpensive and that the coupling is easy to mount. An additional advantage is that it is mounted from behind, i.e., the coupling unit is inserted into the hole of the holder block from the hose-connection side, which allows premounting of connection couplings, elbow couplings or hydraulic hoses before the installation. The problem here is that the joint does not become entirely free of play, which results in wear and possible fracture of the circlip in the case of pulsations and high-pressure surges. Has clear limitations at large separation forces in the hydraulic system.
Another alternative is that the coupling unit is screw-mounted from behind. This may be done by the fact that each coupling unit is individually tightened or that a plurality of coupling units are collectively tightened by means of a fixing plate that is connected in the holder block. These two attachments provide a stable joint that resists pulsations and vibrations well. The disadvantage is that it is hard to gain access in repair mounting out in the field. Furthermore, in the case of individual mounting, it is often too little space to get a sufficient dimension of the attachment. The latter problem is avoided in the case of collective attachment, but here, on the other hand, major problems occur when changing only one coupling.
A third method is to attach the coupling unit in a screw-mounted fashion by a lock nut in the nose end. This is a good method since it provides a joint that is stable and free of play and resists pulsations and vibrations well. Properly dimensioned, it also provides a strong joint that resists large separation forces in the hydraulic system. An additional advantage is that the coupling is mounted from behind, which allows premounting of elbow couplings, pipe joints or hydraulic hoses before the installation. The disadvantage is that this method requires a relatively large space to have room for a properly dimensioned lock nut and mounting tools in order to mount/dismount the coupling.
The hydraulic coupling device according to the present invention is of the type that corresponds to the last-mentioned alternative.
A purpose of the present invention is to overcome the disadvantages associated with such a hydraulic coupling device.